1. Field of the Invention
This invention relates to cartridge assemblies of the type used to record data on a magnetizable medium, usually in the form of a thin, pliable disk, sometimes referred to as a "floppy" disk, and particularly to the jacket that encloses the magnetizable disk.
2. Description of the Prior Art
The prior art related to the subject invention is believed found in Class 360, sub-classes, 133, 135, 99 and 128; and Class 428, sub-class 900. A search through this field of search has indicated the existence of four United States patents as follows:
U.S. Pat. No. 4,038,693 PA1 U.S. Pat. No. 4,375,658 PA1 U.S. Pat. No. 4,354,213 PA1 U.S. Pat. No. 4,251,843
U.S. Pat. No. 4,038,693 relates to a jacket material of high electrical insulating characteristics having an inside surface of electrically conductive material for draining away electrostatic charge from the enclosed floppy disk. The jacket may be fabricated from flexible vinyl sheet material such as polyvinyl chloride, but preferably, polyvinyl chloride acetate. There is no teaching in this patent of the use of a polyester as the jacket material.
U.S. Pat. No. 4,251,843 relates to a disk jacket fabricated from polyvinyl chloride. There is no teaching in this patent of the use of polyester as the material from which a floppy disk jacket might be fabricated.
U.S. Pat. No. 4,354,213 teaches that polyester as a lubricant is used in the fabrication of the floppy disk, and suggests the use of polyester fibers for the formation of an antistatic liner normally found in the inside of a floppy disk jacket. Nothing is found in this patent to suggest the use of polyester as the material from which the jacket as a whole should or could be fabricated.
U.S. Pat. No. 4,375,658 teaches the use of Lexan polycarbonate material for the floppy disk jacket. There is no teaching in this patent of a floppy disk jacket fabricated from polyester material.
It will be readily seen from the above discussion of the prior art that polyvinyl chloride, polyvinyl chloride acetate and Lexan polycarbonate materials are commonly used in the fabrication of floppy disk jackets. It has been found, however, that polyvinyl chloride and polyvinyl chloride acetate jackets are highly susceptible to warpage due to heat cycling, thus rendering the jackets and the data contained on the disk within the jacket substantially useless for several reasons. One such reason is the amount of torque required to rotate the disk within the warped jacket. Obviously, if the jacket warps, frictional forces are imposed on the disk that are not ordinarily present. The amount of force (torque) required to rotate the disk is important because if too much torque is required the disk will wear more rapidly, it will not remain perfectly flat during operation, thus affecting the reliability of the data "written" on the disk or "read" from it. For instance, the starting torque recommended to the American National Standards Institute, Inc. amounts to only 1.42 ounce-force-inches for a two-sided double-density unformatted 5.25 inch flexible disk cartridge. The running torque for the same disk is recommended at no more than 4.6 ounce-force-inches. For a one-sided single-density unformatted 5.25 inch flexible disk cartridge the running torque is recommended at no more than 3.5 ounce-force-inches. Accordingly, it is one of the objects of the present invention to provide a floppy disk jacket and floppy disk assembly that operates within these parameters, despite temperature cycling to temperatures above 125.degree. F. at which the polyvinyl chloride-type jackets start a softening process that is detrimental to the reliability of the assembly in use.
Surprisingly, to my knowledge, polyester materials have not been used for the fabrication of floppy disk jackets despite some rather important disadvantages of the polyvinyl chloride materials. At least one of these disadvantages is the use of plasticizers in the polyvinyl chloride materials to render them pliable. It has been found that the plasticizers migrate out of the material over time, contributing to embrittlement of the material and a greater tendency to warp and stay warped when subjected to heat cycling. For instance, the American National Standards Institute, Inc. recommends that the disk shall withstand operation and storage temperatures at the surface of the disk cartridge in the range from 50.degree. F. to 125.degree. F. at a relative humidity of 8% to 80%. It will of course be understood that in many of our southern states the upper limit of this temperature range is easily exceeded in the trunk of an automobile, where cartridge assemblies are apt to be stored. While the heat may not injure the disk itself, it wreaks havoc with the jacket within which it is enclosed. Accordingly, it is another object of the invention to provide a jacket for a floppy disk cartridge assembly that is dimensionally stable and remains flat even at high temperatures that would destroy a jacket fabricated from polyvinyl chloride material.
A still further object of the invention is the provision of a jacket for a floppy disk cartridge assembly in which the jacket is formed from a polyester material.
Yet another object of the invention is the fabrication of a jacket for a floppy disk wherein the tabs conventionally folded over the body of the jacket and secured thereto to form the jacket are eliminated, thus minimizing the edge thickness of the jacket.
Still another object of the invention is the provision of a floppy disk jacket fabricated from polyester material and having three side edges fused together to form a pocket having one open side into which a floppy disk may be inserted.
Another object of the invention is the provision of a floppy disk jacket structure that lends itself to mass production techniques.
Another object of the invention is the provision of a floppy disk jacket fabricated from polyester and having a fiber liner secured to the inside surfaces of the sides of the jacket.
Conventional floppy disk jackets are fabricated from polyvinyl blanks that are folded medianly to form two sides of the jacket, with integral tabs on three side edges of one of the sides foldable in such a way that they overlap the other side, to which they are secured by heat staking or adhesive. After formation of the pocket in this manner, the floppy disk is inserted into the open side of the jacket and the final tab is folded over and secured to enclose the floppy disk. Accordingly, it is one of the objects of the present invention to eliminate the necessity of folding the floppy disk jacket material, and to eliminate the necessity of providing or folding edge tabs in the jacket material to form a pocket.
The invention possesses other objects and features of advantage, some of which, with the foregoing, will be apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiment illustrated and described since it may be embodied in various forms within the scope of the appended claims.